This invention relates to a nonwoven fabric used as a wiping medium of a magnetic recording medium known as a computer diskette, which comprises a flexible magnetic recording disk contained in an envelope, having a wiping fabric attached therein.
The importance of nonwoven fabrics in computer diskettes is now recognized as being more than a protective fabric to minimize wear or abrasion of the magnetic media. The wiping action of the fabric is important to the function of the floppy disk medium which stores information for use in a disk drive. The wiping action of the fabric is also important because debris that may interfere with the information transfer at the read-write head of the computer disk drive, is ideally removed and entrapped by a wiping fabric. Debris originates from many sources such as; the diskette manufacturing process; the envelope itself; the action of the read-write head on the magnetic disk; external environment; and, abrasion of the magnetic disk, caused by abrasive fibers used in making nonwoven wiping fabrics.
While there is a demonstrated need for a wiping medium to keep the magnetic disk clean in order to reduce errors in the transmission of information onto or from said magnetic disk, the prior art does not indicate what characteristics are needed in a wiping fabric to perform this task.
The fabric that would perform such a task must be constructed in such a manner that fibers used in the fabric would not themselves produce debris in the process of making the fabric. The fibers used therein should not be abrasive to the magnetic disk in which it would come in contact. If debris created by abrasion is not removed or if the wiping fabric abrades the magnetic disk producing foreign particles then said foreign particles will impinge upon the surface, or remove the surface of the magnetic disk. Such abrasion or removal of the surface causes errors in the information that is being transferred from or onto a magnetic disk, and a misreading of said information would take place.
U.S. Pat. No. 3,668,658 discloses a magnetic record disk cover wherein any porous low friction anti-static material is used to wipe the surface of the magnetic media.
In addition, U.S. Pat. No. 4,239,828 discloses a self-lubricating magnetic recording diskette, wherein a nonwoven porous tissue-like material is impregnated with a specific additive to lubricate the surface of the magnetic media to prolong the life of the disk.
Although the prior art outlines the need for a wiping fabric to keep the magnetic disk or media used in computer diskettes free from foreign particles in order to reduce errors in information transfers, it is only concerned with enveloping the magnetic disk in a cover to reduce the amount of external contamination that may settle on the magnetic record surface, or the lubricating of the surface of the magnetic disk to reduce contamination and extend the life of said magnetic disk. However, the prior art does not take into account other problems that exist in providing error free performance in the transfer of information onto or from a magnetic disk. There is also a problem of debris caused by loose particles inherent in the use of certain fibers in nonwoven fabrics that may be used as wiping mediums in a recording diskette. Another problem is caused by abrasiveness in the pressure pad area of the computer diskette. For the purpose of this invention a pressure pad is defined as an external mechanism which is part of the information recording system being used. One such system operates by sending an electric impulse to a solenoid, which in turn moves a pressure pad into a position adjacent the read-write head of the computer disk drive and puts it in contact with the computer diskette, thereby exerting pressure onto the diskette envelope and pushing the envelope and attached wiping medium onto the magnetic medium, allowing the wiping medium to clean the magnetic disk, while information is being transferred. The pressure pad exerts substantial pressure on the wiping fabric, which is in contact with the magnetic disk's surface, in order to entrap debris created by the read-write head. The pressure exerted by the pressure pad presents a problem. This problem develops when pressure exerted by the pressure pad on the computer diskette is transferred to the wiping fabric. This combination of force and fabric friction within a computer diskette may possibly slow the magnetic disk, thus causing poor transfer of information from the recording system to the disk. Additionally, as mentioned before hand, the pressure of the read-write head on the magnetic disk contributes to abrasion of said disk due to the numerous cycles that the disk has to go through with the read-write head pressing down on said magnetic disk causing debris. Another problem that exists in wiping fabrics, which is caused in the production of these fabrics, is dimensional creep. Dimensional creep is a disadvantage because it changes dimensions of a fabric for example; dimensional creep exists when a fabric is altered, by cutting it while it is under tension. If the fabric remains under tension its dimensions remain the same as they were when cut. Once the tension is removed from the fabric and it relaxes, its dimensions change due to the fabric's memory of what its dimensions were prior to being put under tension. Thus when the fabric is cut to mate with diskette components it does not retain its dimensions after the tension is removed, and may be rejected. The present invention substantially overcomes all the disadvantages prevalent in the prior art by providing a fabric that significantly reduces errors in the transmission of information onto or from a computer magnetic disk, by reducing foreign contamination and providing a fabric that is: substantially free of fiber debris; non-abrasive; highly compressible; and has dimensional stability. These characteristics are needed in a liner fabric, to overcome problems associated with providing error free transfer of information from or onto a magnetic disk.